Piezoelectric ceramic composition and piezoelectric ceramic electronic component

ABSTRACT

A piezoelectric ceramic includes a main constituent represented by the general formula {(1−x) (K 1-a-b Na a Li b )(Nb 1-c Ta c )O 3 }−xM2M4O 3 }, and as accessory constituents, 2α mol of Na, (α+β) mole of an M4′ element, and γ mol of Mn with respect to 100 mol of the main constituent, where 0.1≦α≦β, 1≦α+β≦10, and 0≦γ≦10, M2 is Ca, Ba, and/or Sr, the M4 element and the M4′ element are Zr, Sn, and/or Hf, 0≦x≦0.06, 0≦a≦0.9, 0≦b≦0.1, and 0≦c≦0.3. Even in the case of using Ni as the main constituent in an internal electrode material of a piezoelectric element and carrying out co-firing, favorable piezoelectric properties can be obtained without defective polarization.

This is a continuation of application Serial No. PCT/JP2009/058486,filed Aug. 30, 2009, the entire contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a piezoelectric ceramic composition anda piezoelectric ceramic electronic component, and more particularly,relates to a lead-free piezoelectric ceramic composition, and apiezoelectric ceramic electronic component using the piezoelectricceramic composition, such as a laminated piezoelectric actuator.

BACKGROUND ART

In recent years, demand has been increased for laminated piezoelectricceramic electronic components such as laminated piezoelectric actuators,which are able to acquire a large amount of displacement even at lowvoltages.

This type of piezoelectric ceramic electronic component is typicallymanufactured in such a way that ceramic green sheets to serve aspiezoelectric ceramic layers and conductive layers to serve as internalelectrodes are stacked alternately and subjected to co-firing.Furthermore, Ni which is relatively easily available at a low price ispreferably used as an internal electrode material.

Also, lead-free piezoelectric ceramic compositions containing no Pb havebeen attracting attention for environmental care, etc. in recent years.In particular, KNbO₃ based piezoelectric ceramic compositions with Klocated as a main constituent at the A site of a perovskite structure(general formula: ABO₃) and Nb located as a main constituent at the Bsite thereof have been researched and developed actively, because theKnbO₃ based piezoelectric ceramic compositions provide relatively highpiezoelectric d constants (piezoelectric strain constants).

For example, Patent Document 1 discloses a piezoelectric ceramiccomposition which has a main constituent represented by the generalformula{(1−x)(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c-d)Ta_(c)Sb_(d))O₃−xM2_(n)M4O₃}.In this formula, M2 represents at least one bivalent metal elementselected from among Ca, Sr, and Ba, and M4 represents at least onetetravalent metal element selected from among Ti, Zr, and Sn, x, a, b,c, d, m, and n respectively fall within the ranges of 0.005≦x≦0.1,0≦a≦0.9, 0≦b≦0.3, 0≦a+b≦0.9, 0≦c≦0.5, 0≦d≦0.1, 0.9≦m≦1.1, and 0.9≦n≦1.1,and at least one specific element selected from among In, Sc, Y, Nd, Sm,Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu is contained in an amount of 0.1 to10 mol in total with respect to 100 mol of the main constituent.

In Patent Document 1, the piezoelectric ceramic composition hascompositional constituents as described above, and thus can be sinteredstably in the atmosphere, thereby allowing for the achievement ofpiezoelectric ceramic electronic components which have a high relativedielectric constant and electromechanical coupling coefficient, and alsohave a high Curie point of Tc and a high piezoelectric d constant.

Patent Document 1: Japanese Patent No. 3945536

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, the piezoelectric ceramic composition in Patent Document 1 hasthe problems of defective polarization and a degraded piezoelectricproperty in the case of using Ni as the internal electrode material.

More specifically, when conductive layers containing Ni as their mainconstituent and the ceramic green sheets which have the compositionalconstituents described in Patent Document 1 are stacked alternately andsubjected to co-firing, the Ni which constitutes the internal electrodematerial will diffuse to the ceramic green sheets during the firing,resulting in the segregation of the M4 element and the formation of asegregated phase such as Ni or Nb, and thereby leading to problems ofdefective polarization and degradation of the piezoelectric properties.

The present invention has been achieved in view of these circumstances,and an object of the present invention is to provide a piezoelectricceramic composition which can provide a favorable piezoelectric propertywithout causing defective polarization even in the case of using Ni foran internal electrode material and co-firing, and a piezoelectricceramic electronic component using the piezoelectric ceramiccomposition, such as a laminated piezoelectric actuator.

Means for Solving the Problem

The present inventors have carried out earnest studies on monovalent andpentavalent—bivalent and tetravalent compositions represented by thegeneral formula {(1−x)KnbO₃−xM2M4O₃}, in order to achieve the objectmentioned above. Then, it has been found that when the same species of atetravalent M4′ element as the M4 present as an accessory constituenttogether with monovalent Na in the composition so as to be equivalent tothe stoichiometric composition or more in terms of mol, it is possibleto prevent the M4 element from being segregated and prevent a segregatedphase such as Ni or Nb from being formed. In addition, it has been alsofound that the addition of a predetermined range of Mn to thecomposition can improve the sinterability in a reducing atmospherewithout forming a segregated phase of Mn. These elements allow for theachievement of a piezoelectric ceramic composition which has a favorablepiezoelectric property without causing defective polarization even inthe case of co-firing with Ni.

The present invention has been achieved based on these findings, and apiezoelectric ceramic composition according to the present inventioncharacteristically includes a main constituent represented by thegeneral formula{(1−x)(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c)Ta_(c))O₃}−xM2M4O₃}, M2 is atleast one of Ca, Ba, and Sr, M4 is at least one of Zr, Sn, and Hf, andx, a, b, and c are respectively 0≦x≦0.06, 0≦a≦0.9, 0≦b≦0.1, and0≦c≦0.3), and as accessory constituents, 2α mol of Na, (α+β) mol of anM4′ element (M4′ represents at least one element of Zr, Sn, and Hf), andγ mol of Mn with respect to 100 mol of the main constituent, wherein α,β, and γ respectively satisfy 0.1≦α≦β, 1≦α+β10, and 0≦γ≦10.

In addition, further earnest studies carried out by the presentinventors have found that the ranges of 2≦γ≦10 for γ and 0.001≦x≦0.06for x can give a more favorable product yield.

More specifically, a feature of the piezoelectric ceramic compositionaccording to the present invention is that γ is 2≦γ≦10.

Furthermore, a feature of the piezoelectric ceramic compositionaccording to the present invention is that x is 0.001≦x≦0.06.

In addition, the study results of the present inventors have found thatthe substitution of part of Nb with Sb in the range of 0.05 mol or lesscan ensure a favorable piezoelectric property, thereby providing adesired piezoelectric ceramic composition depending on the intended use.

More specifically, another feature of the piezoelectric ceramiccomposition according to the present invention is that part of Nbcontained in the main constituent is substituted with Sb in the range of0.05 mol or less.

Furthermore, further earnest studies of the present inventors have foundthat a predetermined amount of specific rare earth element M3 containedcan make a further improvement in sinterability, and thus provide apiezoelectric ceramic composition which can prevent a piezoelectricceramic electronic component from being strained.

More specifically, another feature of the piezoelectric ceramiccomposition according to the present invention is that at least onespecific rare earth element selected from the group of Sc, In, Yb, Y,Nd, Eu, Gd, Dy, Sm, Ho, Er, Tb, Lu, La, and Pr is contained in the rangeof 5.0 mol or less with respect to 100 mol of the main constituent.

Furthermore, another feature of the piezoelectric ceramic compositionaccording to the present invention is that at least 0.1 mol of thespecific rare earth element is contained with respect to 100 mol of themain constituent.

In addition, a piezoelectric ceramic electronic component according tothe present invention include a piezoelectric ceramic body with internalelectrodes and piezoelectric ceramic layers stacked alternately andsintered; and external electrodes formed on the surface of thepiezoelectric ceramic body, wherein the piezoelectric ceramic layers areformed from the piezoelectric ceramic composition.

In addition, another feature of the piezoelectric ceramic electroniccomponent according to the present invention is that the internalelectrodes contain Ni as their main constituent.

Advantages of the Invention

The piezoelectric ceramic composition according to the present inventioncan prevent the M4 element from being segregated, and prevent asegregated phase such as Ni or Nb from being formed, even in the case ofco-firing with the internal electrode material containing Ni as its mainconstituent. Furthermore, the presence of Mn even allows for theachievement of a piezoelectric ceramic composition which has a favorablepiezoelectric property without forming a segregated phase of Mn, andthus, without causing defective polarization.

In addition, the substitution of part of Nb contained in the mainconstituent with Sb in the range of 0.05 mol or less thus allows for theachievement of a piezoelectric ceramic composition which has favorablepiezoelectric properties for its intended uses.

Further, the presence of the specific rare earth element contained inthe range of 0.1 mol to 5.0 mol with respect to 100 mol of the mainconstituent thus causes no warpage even after sintering, therebyallowing for the achievement of a piezoelectric ceramic composition withfavorable sinterability, in addition to the advantageous effectdescribed above.

In addition, the piezoelectric ceramic electronic component according tothe present invention includes a piezoelectric ceramic body withinternal electrodes and piezoelectric ceramic layers stacked alternatelyand sintered; and external electrodes formed on the surface of thepiezoelectric ceramic body, where the piezoelectric ceramic layers areformed from the piezoelectric ceramic composition in the piezoelectricceramic electronic component. Thus, sintering can be completed even inthe case of using a material containing Ni as its main constituent as aninternal electrode material, and a low-cost and highly-practicalpiezoelectric ceramic electronic component can be obtained which has anexcellent piezoelectric property, without causing defectivepolarization.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a cross-sectional view illustrating an embodiment of alaminated piezoelectric actuator as a piezoelectric ceramic electroniccomponent according to the present invention.

FIG. 2 is a perspective view of a ceramic green sheet obtained in theprocess of manufacturing the piezoelectric actuator.

FIG. 3 is a perspective view of the piezoelectric actuator.

FIG. 4 is a mapping image for sample number 2.

FIG. 5 is a mapping image for sample number 1.

FIG. 6 is a mapping image for sample number 7.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, embodiments of the present invention will be described in detail.

A piezoelectric ceramic composition as an embodiment of the presentinvention is represented by the following general formula (A).100{(1−x)(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c)Ta_(c))O₃−xM2M4O₃}+2αNa+(α+β)M4′+γMn  (A)

In the formula, M2 represents at least one element selected from Ca, Ba,and Sr with a valence of 2, and M4 and M4′ each represent at least oneelement selected from Zr, Sn, and Hf with a valence of 4.

In addition, x, a, b, c, α, β, and γ satisfy the following mathematicalformulas (1) to (7):0≦x≦0.06  (1)0≦a≦0.9  (2)0≦b≦0.1  (3)0≦c≦0.3  (4)0.1≦α≦β  (5)1≦α+β≦10  (6)0≦γ≦10  (7)More specifically, the piezoelectric ceramic composition contains Na, anM4′ element and Mn so as to satisfy the mathematical formulas (5) to (7)with respect to 100 mol of a main constituent represented by thefollowing general formula (B). This composition does not exhibitdefective polarization even in the case of using, as the internalelectrodes, a conductive material containing Ni as its main constituent,thus allowing a piezoelectric ceramic composition which has a favorablepiezoelectric property.(1−x)(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c)Ta_(c))O₃−xM2M4O₃  (B)

When conductive layers containing Ni as their main constituent andceramic green sheets which have the composition represented by thegeneral formula (B) are stacked alternately and subjected to co-firing,Ni in the conductive layers will diffuse to the ceramic green sheets,resulting in the segregation of the M4 element and the formation of asegregated phase such as Ni or Nb in the ceramic sintered body afterfiring, which thereby leads to defective polarization and degradation ofthe piezoelectric properties.

However, study results of the present inventors have found that when Naand the same species of the specified M4′ element as the M4 element areblended so that the perovskite structure has an excessive amount of Bsite relative to the stoichiometric composition as a whole, theformation of the segregated phase can be reduced, thereby preventingdefective polarization and degradation of piezoelectric properties.

More specifically, when the main constituent raw materials mixed with Naand the M4′ element are subjected to firing, Na₂M4′O₃ is generated inthe process of the firing. Then, this Na₂M4′O₃ reacts with the M4′element, Ni, etc. which are present in excess, to produce aperovskite-type composite oxide, 2NaM4′O_(2.5) as a solid solution inthe main constituent. This solid solution of 2NaM4′O_(2.5) in the mainconstituent allows the formation of a segregated phase to be reduced.

In addition, when the molar quantity β of the M4′ element is greaterthan the molar quantity a consumed in the reaction with Na with respectto the total content molar quantity (α+β) of the M4′ element, K can beprevented from being segregated at crystal grain boundaries.

More specifically, Na and the M4′ element react during the process ofthe firing to produce Na₂M4′O₃ as a solid solution in the mainconstituent as described above, and in this case, it is supposed thatmost of Na is present as a solid solution at the A site, whereas most ofM4′ is present as a solid solution at the B site. Thus, the part α ofthe molar quantity of the M4′ element is greater than the part β of themolar quantity thereof and results in considerable Na₂M4′O₃ begenerated, and causes an excessive amount of Na ions to be present as asolid solution at the A site. For this reason, there is a possibilitythat K ions, which have a larger in ion radius than Na ions, will besegregated as a segregated phase at the crystal grain boundaries, andthereby cause defective polarization and degradation of thepiezoelectric properties.

From the viewpoint of prevention of segregation of K at crystal grainboundaries, the partial content molar quantity β of the M4′ element istherefore required to be at least equivalent to the partial contentmolar quantity α.

It is to be noted that the crystalline microstructure of thepiezoelectric ceramic composition is not particularly limited as long asthe general formula (A) satisfies the mathematical formulas (1) to (7).For example, part of Na or the M4′ element added as an accessoryconstituent may be present as a solid solution at the A site, whereasthe rest may be present as a solid solution at the B site. Furthermore,part of the accessory constituent may be present as a solid solution inthe main constituent, whereas the rest may be present at crystal grainboundaries or crystal triple points.

The M4 element and the M4′ element may be any of Zr, Sn, and Hf. The M4element and the M4′ element may be composed of the same element, or maybe formed from different species of these elements. For example, the M4element and the M4′ element may be respectively composed of Zr and Sn,or the M4 element and the M4′ element may be both composed of Zr.

Next, the reasons why the x, a, b, c, α, and β are limited as in themathematical formulas (1) to (7) will be described.

(1) x

The KNbO₃ based composition may have M2M4O₃ present therein as a solidsolution to thereby allow for the achievement of a favorablepiezoelectric property based on the intended use. However, if the M2M4O₃in the main constituent has a solid solubility molar ratio x of greaterthan 0.06, there is a possibility that the excessive solid solubilityamount of M2M4O₃ will degrade the piezoelectric property, and lead to adecrease in Curie point Tc.

Thus, the amounts of the KNbO₃ based compound and M2M4O₃ in the presentembodiment are adjusted so that the solid solution molar ratio x is0≦x≦0.06.

It is to be noted that if the solid solution molar ratio x of M2M4O₃ isless than 0.001, there is a possibility that defectives without adesired piezoelectric property can be easily formed and lead to adecrease in product yield.

Therefore, the solid solution molar ratio x of M2M4O₃ in the mainconstituent is preferably 0.001≦x≦0.06 in view of product yieldconsiderations.

(2) a, b

Part of K in the KNbO₃ based composition is also preferably substitutedwith other alkali metals such as Na and Li, if necessary. However, whenthe substitution molar amount a of Na greater than 0.9 or thesubstitution molar amount b of Li greater than 0.1, there is possibilitythat degradation of the piezoelectric properties will be caused.

Thus, the amounts of the compositional constituents in the presentembodiment are adjusted so that the molar amounts a and b are 0≦a≦0.9and 0≦b≦0.1.

(3) c

Part of Nb in the KNbO₃ based compound is also preferably substitutedwith Ta, if necessary. However, there is a possibility that asubstitution molar amount a of Ta greater than 0.3 will lead todegradation of the piezoelectric property, and lead to a decrease inCurie point Tc.

Thus, the amounts of the compositional constituents in the presentembodiment are adjusted so that the molar amount c is 0≦c≦0.3.

(4) α, β

As described above, the combined Na and M4′ amount is such that theperovskite structure has a somewhat excessive amount of B site relativeto the stoichiometric composition as a whole, which can reduce theformation of a segregated phase, and it is thereby possible to suppressdefective polarization and piezoelectric property degradation.

However, if the molar quantity α of the M4′ element totally consumed inthe reaction with Na is less than 0.1 mol with respect to 100 mol of themain constituent, the amount of Na₂M4′O₃ produced in the process of thefiring will be reduced, thereby failing to fully produce the desiredeffect, and failing to fully reduce the segregated phase describedabove.

If the total content molar quantity (α+β) of the M4′ element is lessthan 1 mol with respect to 100 mol of the main constituent, the smalltotal content molar quantity (α+β) fails to fully produce the desiredeffect, and thus fails to fully reduce the segregated phase describedabove.

On the other hand, there is a possibility of degradation of apiezoelectric property if the total content molar quantity (α+β) of theM4′ element is excessively greater than 10 mol with respect to 100 molof the main constituent.

In addition, if the unreacted molar quantity β of the M4′ element isless than the reacted molar quantity α as described above, a segregatedphase of K is unfavorably formed.

Thus, Na and the M4′ element are present in the present embodiment sothat the content molar quantity 2α of Na, the partial content molarquantities α, β of the M4′ element, and the total content molar quantity(α+β) of M4′ satisfy 0.1≦α≦β and 1≦α+β≦10 with respect to 100 mol of themain constituent.

(5) γ

Mn can be contained in the piezoelectric ceramic composition to allowthe sinterability in a reducing atmosphere to be improved. However, ifthe content molar quantity γ of Mn is excessively greater than 10 molwith respect to 100 mol of the main constituent, there is a possibilitythat a segregated phase of Mn will be formed and lead to defectivepolarization and piezoelectric property degradation.

In the present embodiment, therefore the additive amount of Mn isadjusted so that the content molar quantity γ is 0≦γ≦10 with respect to100 mol of the main constituent.

It is to be noted that when the content molar quantity γ of Mn is lessthan 2 mol with respect to 100 mol of the main constituent, there is apossibility that defectives without the desired piezoelectric propertywill be easily formed and lead to a decrease in product yield.

In view of product yield, therefore, the content molar quantity γ of Mnwith respect to 100 mol of the main constituent is preferably 2≦γ≦10.

In the present embodiment, the compositional constituents were preparedso that the general formula (A) satisfies the mathematical formulas (1)to (7), as described above. Thus, even when a conductive materialcontaining Ni as its main constituent is used for the internal electrodematerial and subjected to co-firing, segregation of the M4 element is soreduced that the formation of a segregated phase such as Ni or Nb isreduced. Furthermore, no segregated phase of Mn will be formed, andaccordingly, a desired piezoelectric ceramic composition can be obtainedwhich suppresses defective polarization or piezoelectric propertydegradation.

It is also preferable in the present invention to add at least onetrivalent specific rare earth element M3 (M3 element) selected from thegroup of Sc, In, Yb, Y, Nd, Eu, Gd, Dy, Sm, Ho, Er, Tb, Lu, La, and Pr,if necessary.

In this case, the piezoelectric ceramic composition is represented bythe following general formula (C).100{(1−x)(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c)Ta_(c))O₃−xM2M4O₃}+2αNa+(α+β)M4′+γMn+δM3  (C)

These M3 elements are present as donors in a solid solution at the Asite of the perovskite structure, and thus believed to have the functionof promoting the solid solubility of Mn and the M4 element and the M4′element acting as acceptors at the B site into crystal grains andkeeping Mn and the M4 element and the M4′ element in the crystal grainsstably. Therefore, the sinterability in a reducing atmosphere is furtherstabilized to allow the ceramic sintered body to resist warpage, andmake it possible to contribute to the improvement in piezoelectricproperty.

When adding the M3 element, the content molar quantity δ thereof ispreferably 5.0 mol or less with respect to 100 mol of the mainconstituent. This is because if the content of the M3 element is greaterthan 5.0 mol with respect to 100 mol of the main constituent, there is apossibility of causing defective sintering to decrease the insulationresistance and thus lead to defective polarization.

In order to fully produce the effect of preventing the ceramic sinteredbody from warpage, the content molar quantity δ of the M3 element ispreferably made at least 0.1 mol with respect to 100 mol of the mainconstituent.

It is to be noted that of the M3 elements, Sc, In, and La have atendency to be slightly inferior in sinterability, and it is thus morepreferable to use at least one selected from the group of Yb, Y, Nd, Eu,Gd, Dy, Sm, Ho, Er, Tb, Lu, and Pr, excluding Sc, In, and La.

Furthermore, part of Nb in the present invention in the main constituentis preferably substituted with Sb, if necessary, and this substitutioncan provide a piezoelectric ceramic composition with a desiredpiezoelectric property.

In this case, the piezoelectric ceramic composition is represented bythe following general formula (D).100{(1−x)(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c-d)Ta_(c)Sb_(d))O₃−xM2M4O₃}+2αNa+(α+β)M4′+γMn+δM3  (D)

In general formula (D), x represents the molar amount of M2M4O₃, and aand b are the amount of Na and Li, respectively, in the alkali metalcontent in (K_(1-a-b)Na_(a)Li_(b)). The number of mols of(K_(1-a-b)Na_(a)Li_(b)) in(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c-d)Ta_(c)Sb_(d)) is the same as that of(Nb_(1-c-d)Ta_(c)Sb_(d)), and the number of mols of M2M4O₃ is the sameas that of M4.

Since Na and M4 (having the same elements as M4′) are present in theaccessory constituents, the content of these should not be included inx. The substitutions described in the preceding paragraph results in{(1−x)(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c-d)Ta_(c)Sb_(d))O₃}−xM2M4O₃} to(1−x)(Nb_(1-c-d)Ta_(c)Sb_(d))−xM2. Accordingly,x=M2/(Nb_(1-c-d)Ta_(c)Sb_(d)). Rewriting this equation using Σ( . . . )to indicate the total of the moles of the elements within the bracketsresults in x=Σ(Ca,Ba,Sr)/(Σ(Nb,Ta,Sb,Ca,Ba,Sr).

The amount of K and the amount of Li (i.e., b) in the alkali metalcontent of (K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c-d)Ta_(c)Sb_(d)) would betheir individual amounts divided by the total amount of Nb, Ta and Sb asin the last paragraph (in order to avoid including the accessory contentof Na). Rewriting b using Σ( . . . ) results in b=Σ(Li)/Σ(Nb,Ta,Sb).

The molar amount of Na in the alkali metal content (i.e., a) isdetermined by subtracting the amounts of K and Li from 1 in order toavoid including the amount of Na in the accessory material. Rewriting1−(K+Li) using Σ( . . . ) results ina=1−(Σ(Li)/(Σ(Nb,Ta,Sb)−(Σ(K)/(Σ(Nb,Ta,Sb)).

In general formula (D), c is the amount of Ta and d is the amount of Sbin (Nb_(1-c-d)Ta_(c)Sb_(d)). Therefore c=Ta/Nb+Ta+Sb and d=Sb/Nb+Ta+Sb.Rewriting using Σ( . . . ) to indicate the total moles of the elementswithin the brackets results in c=Σ(Ta)/Σ(Nb,Ta,Sb), andd=Σ(Sb)/Σ(Nb,Ta,Sb).

General formula (D) shows that the accessory constituents contain 2αmols of Na, α+β mols of M4′, γ mols of Mn and δ mols of M3 with respectto 100 moles of the main constituent.

As discussed above, the main constituent can be simplified to(1−x)(Nb_(1-c-d)Ta_(c)Sb_(d))−xM2, so that 100 mols of the mainconstituent is the same as the total moles of Nb, Ta, Sb and M2, orstated alternatively, Σ(Nb,Ta,Sb,Ca,Ba,Sr). Therefore, using Σ( . . . ),γ=100×(Σ(Mn)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)), andδ=100×(Σ(Sc,In,Yb,Y,Nd,Eu,Gd,Dy,Sm,Ho,Er,Tb,Lu,La,Pr)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)).

Since there is Na in both the main and accessory constituents, the Naamount in the accessory constituents in proportion to the main componentcan be determined from the amount of total alkali metals,Σ(K,Na,Li))/Σ(Nb,Ta,Sb,Ca,Ba,Sr), and subtracting the amount of Nb, Ta,and Sb, Σ(Nb,Ta,Sb)/Σ(N,Ta,Sb,Ca,Ba,Sr). Consequently 2α can berepresented by100×(Σ(K,Na,Li))/Σ(Nb,Ta,Sb,Ca,Ba,Sr)−Σ(Nb,Ta,Sb)/Σ(N,Ta,Sb,Ca,Ba,Sr)),andα=50×(Σ(K,Na,Li))/Σ(Nb,Ta,Sb,Ca,Ba,Sr)−Σ(Nb,Ta,Sb)/Σ(N,Ta,Sb,Ca,Ba,Sr)).

As noted above, α+β mols of M4′ with respect to 100 moles of the mainconstituent can be obtained by subtracting the amount of M2 (Ca, Ba, Sr)from that of M4 (Zr, Sn, Hf), and thus, using the Σ( . . . ) system, iswritten asα+β=100×(Σ(Zr,Sn,Hf)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)−Σ(Ca,Ba,Sr)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)).

In the case of substituting part of Nb with Sb in place of Ta, theamount is preferably adjusted so that the substitution molar quantity ofSb is 0.05 mol or less, that is, 0≦d≦0.05. This is because there is apossibility that a substitution molar quantity d of Sb greater than 0.05will be excessive and lead to degradation of sinterability.

Next, a piezoelectric ceramic electronic component will be describedwhich is manufactured with the use of the piezoelectric ceramiccomposition.

FIG. 1 is a cross-sectional view illustrating an embodiment of alaminated piezoelectric actuator as an example of piezoelectric ceramicelectronic component according to the present invention. The laminatedpiezoelectric actuator includes a piezoelectric ceramic body 1, andexternal electrodes 2 (2a, 2b) composed of a conductive material such asAg formed on both ends of the piezoelectric ceramic body 1. The ceramicbody 1 is composed of piezoelectric ceramic layers composed of thepiezoelectric ceramic composition according to the present invention andinternal electrodes 3 (3a to 3g) formed from a conductive materialcontaining Ni as its main constituent, which are stacked alternately andsintered.

In the laminated piezoelectric actuator, the internal electrodes 3a, 3c,3e, and 3g each have one end electrically connected to one externalelectrode 2a, whereas the internal electrodes 3b, 3d, and 3f each haveone end electrically connected to the other external electrode 2b. Thus,the laminated piezoelectric actuator is displaced by the longitudinalpiezoelectric effect in the stack direction indicated by an arrow X,when a voltage is applied between the external electrode 2a and theexternal electrode 2b.

Next, a method for manufacturing the laminated piezoelectric actuatorwill be described in detail.

First, a compound containing K, a compound containing Nb, a compoundcontaining an M4 element, and compound containing an M4′ element areprepared as ceramic raw materials, and further, a compound containing anM2 element is prepared. In addition, a compound containing Na, acompound containing Li, and a compound containing Ta, a compoundcontaining Sb, a compound containing Mn and a compound containing an M3element are prepared. It is to be noted that the forms of the compoundsmay be any of oxides, carbonates, and hydroxides.

Next, the ceramic raw materials mentioned above are weighed inpredetermined amounts so that the final product satisfies the generalformula (A), and these weighed materials are then put into a grindingmill, such as a ball mill or a pot mill, with a grinding medium such asPSZ (partially-stabilized zirconia) balls therein, and wet groundsufficiently with a solvent such as ethanol, thereby providing amixture.

Then, the mixture is dried, and subjected to synthesis calcination at apredetermined temperature (for example, 850° C. to 1000° C.) to obtain acalcined material.

Next, the calcined material thus obtained is disintegrated (ground),provided with an organic binder and a dispersant, and wet mixed in aball mill with pure water or the like as a solvent to obtain a ceramicslurry. Then, a forming process is carried out with the use of a doctorblade method or the like to produce ceramic green sheets.

A conductive paste for internal electrodes, which contains Ni as itsmain constituent, is used to carry out screen printing onto the ceramicgreen sheets 4 (4a to 4g) as shown in FIG. 2, thereby forming conductivelayers 5 (5a to 5g) in a predetermined shape.

Next, the ceramic green sheets 4a to 4g with the conductive layers 5a to5g formed thereon are stacked, sandwiched by ceramic green sheets 6a, 6bwhich have no conductive layers 5a to 5g on them, and pressure bonded,thereby producing a ceramic laminate of the conductive layers 5a to 5gand the ceramic green sheets 4a to 4g stacked alternately. This ceramiclaminated is then cut into a predetermined size, housed in an aluminasheath and subjected to a binder removal treatment at a predeterminedtemperature (for example, 250° C. to 500° C.), and then fired at apredetermined temperature (for example, 1000° C. to 1160° C.) under areducing atmosphere to form a dielectric ceramic body (ceramic sinteredbody) 1 with the internal electrodes 3a to 3g buried therein.

A conductive paste for external electrodes, which is composed of Ag,etc., is applied to both ends of the piezoelectric ceramic body 1, andsubjected to a baking treatment at a predetermined temperature (forexample, 750° C. to 850° C.) to form external electrodes 2a and 2b asshown in FIG. 3. A predetermined polarization treatment is then carriedout thereby to produce a laminated piezoelectric actuator. It is to benoted that the external electrodes 2a and 2b may have favorableadhesion, and the external electrodes 2a and 2b may be formed, forexample, by a thin film forming method such as a sputtering method or avacuum deposition method.

As described above, the laminated dielectric actuator has the ceramicgreen sheets (ceramic layers) 4 formed from the piezoelectric ceramiccomposition and the internal electrodes containing Ni as their mainconstituent, and thus, a low-cost and highly-practical piezoelectricceramic electronic component can be obtained which has a favorablepiezoelectric properties, without causing defective polarization.

It is to be noted that the present invention is not limited to theembodiment described above. For example, the M2 element may include atleast any one of Ca, Sr, and Ba, and the M2 element may include otherbivalent elements, for example, Mg. More specifically, Mg is likely tobe present as a solid solution in Ca, Sr, or Ba in crystal grains, butwill not affect the property.

Next, examples of the present invention will be described specifically.

EXAMPLE 1

In Example 1, various types of samples which are different in thecontent molar quantity 2α of Na, the total content molar quantity (α+β)of the M4′ element, and the content molar quantity γ of Mn weremanufactured, and piezoelectric properties and Curie point Tc evaluated.

First, K₂CO₃, Na₂CO₃, Li₂CO₃, Nb₂O₅, CaCO₃, SrCO₃, BaCO₃, ZrO₂, SnO₂,HfO₂, MnCO₃, and Yb₂O₃ were prepared as ceramic raw materials.

Then, the materials were weighed so that the M2 element, the M4 element,the M4′ element, α, β, and γprovided compositions as shown in Table 1 inthe general formula[100{0.98(K_(0.45)Na_(0.53)Li_(0.02))NbO₃−0.02M2M4O₃}+2αNa+(α+β)M4′+γMn+0.5Yb].

Then, these weighed materials were put into a pot mill with PSZ ballstherein, and wet mixed while rotating the pot mill with ethanol as asolvent for about 90 hours. The obtained mixtures were dried, and thensubjected to calcination at a temperature of 900° C. to obtain calcinedmaterials.

After disintegrating these calcined materials, the calcined material wasput in a pot mill along with a binder, a dispersant, and pure water, aswell as PSZ balls, wet mixed while rotating the pot mill, and thensubjected to a forming process with the use of a doctor blade method toobtain ceramic green sheets each having a thickness of 120 μm.

A conductive paste for internal electrodes was prepared using Ni as aconductive material. This conductive paste for internal electrodes wasused to form conductive layers in a predetermined pattern on the ceramicgreen sheets in accordance with a screen printing method. Then, apredetermined number of the ceramic green sheets with the conductivelayers formed were stacked, sandwiched on the top and bottom by ceramicgreen sheets with no conductive layers formed thereon, and pressurizedat a pressure of about 2.45×10⁷ Pa for pressure bonding to produce aceramic laminated compact.

The ceramic laminated compact was fired at a temperature of about 1100°C. for 2 hours in a reducing atmosphere with the equilibrium oxygenpartial pressure for Ni/NiO adjusted to the reducing side by 0.5,thereby manufacturing a piezoelectric ceramic body (ceramic sinteredbody).

External electrodes composed of a Ni—Cu alloy were then formed bysputtering onto both principal surfaces of the piezoelectric ceramicbody, and then, an electric field of 3.0 kV/mm was applied to thepiezoelectric ceramic body in insulating oil at 80° C. for 30 minutes tocarry out a polarization treatment.

After that, the piezoelectric ceramic bodies were cut into rectangularshapes of 15 mm in length, 3 mm in width, and 0.7 mm in thickness sothat the external electrodes were located on the end surfaces, therebymanufacturing samples of sample number 1 to 22.

Next, the longitudinal electromechanical coupling coefficient k₃₁,piezoelectric constant d₃₃, and Curie point Tc were measured for theserespective samples of sample numbers 1 to 22.

The longitudinal electromechanical coupling coefficient k₃₁ was obtainedby a resonance-antiresonance method with the use of an impedanceanalyzer.

The piezoelectric constant d₃₃ was obtained from the amount of chargegenerated and the number of layers stacked when a d₃₃ meter was used toapply a force of 0.25 N_(rms).

The Curie point Tc was obtained by measuring temperature characteristicsof relative dielectric constant with the use of an impedance analyzerand calculating the maximum temperature for the relative dielectricconstant.

Table 1 shows the constituent compositions and the measurement resultsfor sample numbers 1 to 22. It is to be noted that the samples wereconsidered non-defective products in the case of having a longitudinalelectromechanical coupling coefficient k₃₁ of 10% or more, piezoelectricconstant d₃₃ of 30 pC/N or more, and Curie point Tc of 150° C. or more.

TABLE 1 100{0.98(K_(0.45)Na_(0.53)Li_(0.02))NbO₃ − 0.02M2M4O₃} + 2αNa +(α + β)M4′ + γMn + 0.5Yb Electromechanical Piezoelectric Curie SampleCoupling Constant d₃₃ point No. M2 M4 M4′ α β α + β γ Coefficient k₃₁(%) (pC/N) Tc (° C.) Remarks  1* Ca Zr Zr 0 5 5 5 — — — DefectivePolarization  2 Ca Zr Zr 1 4 5 5 24.1 183 230  3 Ca Zr Zr 2.5 2.5 5 5 20134 230 —  4 Ca Zr Zr 0.5 4.5 5 5 22.1 143 230 —  5 Ca Zr Zr 0.1 4.9 5 515.2 62 230 —  6* Ca Zr Zr 0.05 4.95 5 5 — — — Defective Polarization 7* Ca Zr Zr 3 2 5 5 7.2 23 230 —  8 Ca Zr Zr 1 2 3 5 18.4 124 300 —  9Ca Zr Zr 0.5 0.5 1 5 18.4 124 300 —  10* Ca Zr Zr 0.5 0.1 0.6 5 — — —Defective Polarization 11 Ca Zr Zr 1 9 10 5 13.2 81 170 —  12* Ca Zr Zr1 14 15 5 7.2 25 100 — 13 Ca Zr Zr 1 4 5 2 16.3 65 250 —  14** Ca Zr Zr1 4 5 1 15.2 33 270 Low Rate of Non-Defective Products  15** Ca Zr Zr 14 5 0 11.1 30 280 Low Rate of Non-Defective Products 16 Ca Zr Zr 1 4 510 13.2 50 210 —  17* Ca Zr Zr 1 4 5 15 6.8 16 200 — 18 Sr Zr Zr 1 2 3 518.9 136 280 — 19 Ba Zr Zr 1 2 3 5 20.7 143 280 — 20 Ca Sn Zr 1 2 3 515.6 55 280 — 21 Ca Hf Zr 1 2 3 5 19 98 280 — 22 Ca Zr Sn 1 2 3 5 14.350 280 — *outside the scope of the present invention **outside preferredscope of the present invention

Sample numbers 1 to 17 are samples manufactured with Ca for the M2element and Zr for the both M4 element and M4′ element.

In sample number 1, a sample containing no Na therein (a is 0),exhibited defective polarization. This is supposed to be because noNa₂ZrO₃ was able to be formed in the process of the firing, and Ni inthe conductive layers thus diffused to the ceramic green sheets duringthe firing, resulting in the segregation of Zr as the M4 element and inthe formation of a segregated phase such as Ni, Mn, or Nb.

In the case of sample number 6, a sample containing Na but with a smallcontent molar quantity 2α of 0.10 mol with respect to 100 mol of themain constituent (0.05 mol with respect to 50 mol of the mainconstituent), the formed Na₂ZrO₃ was not sufficient to reduce thesegregated phase in the process of the firing, and as in the case ofsample number 1, exhibited defective polarization.

The partial content molar quantity a of Zr in the case of sample number7 was greater than the partial content molar quantity β thereof, causinga segregated phase of K, and resulting in the degraded piezoelectricproperties of an electromechanical coupling coefficient k₃₁ of 7.2%,which is less than the desired 10%, and a piezoelectric constant d₃₃ of23 pC/N, which is less than 30 pC/N.

In the case of sample number 10, there was defective polarization,because of the small total content molar quantity (α+β) of Zr of 0.6 molwith respect to 100 mol of the main constituent.

The excessive total content molar quantity (α+β) of Zr of 15 mol withrespect to 100 mol of the main constituent in the case of sample number12, caused the degraded piezoelectric property of an electromechanicalcoupling coefficient k₃₁ of 7.2%, which is less than 10%, and apiezoelectric constant d₃₃ of 25 pC/N, which is less than 30 pC/N.

In the case of sample number 17, a segregated phase of Mn was present,because of the excessive content molar quantity γ of Mn of 15 mol withrespect to 100 mol of the main constituent. Thus, such a degradedpiezoelectric properties were realized, namely an electromechanicalcoupling coefficient k₃₁ of 6.8%, which is less than 10%, and apiezoelectric constant d₃₃ of 16 pC/N, which is less than 30 pC/N.

In contrast to these samples, the partial content molar quantity α of Zrconsumed in the reaction with Na is 0.1 mol or more, and the partialcontent molar quantity β of Zr is equivalent to the partial contentmolar quantity α or more, and the total content molar quantity (α+β)falls within the range of 1 to 10 mol in the case of sample numbers 2 to5, 8 to 9, 11, and 13 to 16. In addition, the content molar quantity γof Mn falls within the range of 0 to 10 mol, and these quantities allfill within the scope of the present invention. As a result, the use ofNi for the internal electrode material and the co-firing did not causedefective polarization, thereby providing favorable piezoelectricproperties, namely an electromechanical coupling coefficient k₃₁ of 10%or more and a piezoelectric constant d₃₃ of 30 pC/N or more, and a Curiepoint Tc of 150° C. or more.

However, the content molar quantity γ of Mn less than 2 mol with respectto 100 mol of the main constituent in the case of sample numbers 14 and15, resulted in only one to three of the 10 samples being able to bedetermined as non-defective products even though they had the samecomposition. Accordingly, it was found that the content molar quantity γof Mn is preferably 2 mol or more with respect to 100 mol of the mainconstituent.

Sample numbers 18 to 22 are samples with different species of elementsas the M2 element, the M4 element, and the M4′ element, where thecontent molar quantity 2α of Na, the total content molar quantity (α+β)of the M4′ element, and the content molar quantity γ of Mn arerespectively 2 mol, 3 mol, and 5 mol with respect to 100 mol of the mainconstituent.

As is clear from sample numbers 18 to 22, no defective polarization wasrealized even in the case of using Sr or Ba in place of Ca as the M2element (sample numbers 18 and 19) or using Sn or Hf in place of Zr asthe M4 element and the M4′ element (sample numbers 20 to 22). Thus, itwas found that laminated piezoelectric ceramic electronic components canbe obtained which have such favorable piezoelectric properties as anelectromechanical coupling coefficient k₃₁ of 10% or more and apiezoelectric constant d₃₃ of 30 pC/N or more, and a Curie point Tc of150° C. or more.

Next, WDX (wavelength dispersive X-ray analyzer) was used to carry outelement mapping for each sample of sample numbers 1, 2, and 7.

FIG. 4 is a mapping image for sample number 2, FIG. 5 is a mapping imagefor sample number 1, and FIG. 6 is a mapping image for sample number 7.

Each of FIGS. 4 to 6 shows mapping images for each of a secondaryelectron image, Nb and Zr in the order of upper left, upper middle, andupper right, shows mapping images for each of Na, Mn, and K in the orderof middle left, center, and middle right, and shows mapping images foreach of Ca, Yb, and Ni in the order of lower left, lower middle, andlower right.

No Na₂ZrO₃ was formed in the process of the firing in the case of samplenumber 1, and thus as shown in FIG. 5, segregated phases are notablyfound for Nb (upper middle), Mn (center), and Ni (lower right). Zr(upper right) is also segregated.

Since the partial content molar quantity α of Zr is greater than thepartial content molar quantity β thereof in the case of sample number 7,a segregated phase of K is formed at crystal grain boundaries, as shownin the middle right of FIG. 6.

In contrast to these samples, it was confirmed that no segregated phaseis formed as shown in FIG. 4 in the case of sample number 2 which iswithin the scope of the present invention.

It was confirmed from FIGS. 4 to 6 and Table 1 that the segregatedphases formed in the ceramic layers have influences on the polarizationtreatment and the piezoelectric properties. Furthermore, thecompositional constituents according to the present invention provide alaminated piezoelectric ceramic electronic component which has favorablepiezoelectric properties without causing defective polarization even inthe case of using Ni for the internal electrode material and carryingout a co-firing.

EXAMPLE 2

In Example 2, various types of samples which differed in the compositionof the main constituent were manufactured using Ca for the M2 elementand Zr for both the M4 element and the M4′ element, and evaluated forpiezoelectric properties and Curie point Tc.

First, K₂CO₃, Na₂CO₃, Li₂CO₃, Nb₂O₅, CaCO₃, ZrO₂, MnCO₃, and Yb₂O₃ wereprepared as ceramic raw materials.

Then, the materials were weighed so that a, b, c, x, β, and γ providedthe compositions shown in Table 2 of the general formula [100{(1−x)(K_(1-a-b)Na_(a)Li_(b))_(m)(Nb_(1-c)Ta_(c))O₃−xCaZrO₃}+2Na+(1+β)Zr+γMn+0.5Yb] where β is 5 or 2, and γ is 3.0 or 1.0.

Then, samples of sample numbers 31 to 42 were manufactured in accordancewith the same method and procedure as in Example 1.

Next, the longitudinal electromechanical coupling coefficient k₃₁,piezoelectric constant d₃₃, and Curie point Tc were measured for theresulting sample numbers 31 to 42, in accordance with the same method asin [Example 1].

Table 2 shows the constituent compositions and the measurement resultsfor sample numbers 31 to 42.

It is to be noted that the samples were determined as non-defectiveproducts in the case of having a longitudinal electromechanical couplingcoefficient k₃₁ of 10% or more, piezoelectric constant d₃₃ of 30 pC/N ormore, and Curie point Tc of 150° C. or more, as in the case of Example1.

TABLE 2 100+55(1 − x) (K_(1−a−b)Na_(a)Li_(b))(Nb_(1-c)Ta_(c))O₃ −xCaZrO₃} + 2Na + (1 + β)Zr + γMn + 0.5Yb Electromechanical PiezoelectricCurie Sample Coupling Constant d₃₃ point No. a b c x β γ Coefficient k₃₁(%) (pC/N) Tc (° C.) Remarks 31 0 0.02 0 0.02 2 5 11.3 53 320 — 32 0.90.02 0 0.02 2 5 12.2 50 320 —  33* 0.95 0.02 0 0.02 2 5 5 24 320 — 340.54 0 0 0.02 2 5 18.5 118 300 — 35 0.54 0.1 0 0.02 2 5 13.4 106 300 — 36* 0.54 0.2 0 0.02 2 5 4.6 21 300 — 37 0.54 0.02 0.3 0.01 2 5 14.4 78180 —  38* 0.54 0.02 0.4 0.01 2 5 5 23 120 —   39*** 0.54 0.02 0 0 2 514 50 400 Low Rate of Non-Defective Products 40 0.54 0.02 0 0.001 2 514.2 68 370 — 41 0.54 0.02 0 0.06 1 2 11.4 80 160 —  42* 0.54 0.02 0 0.11 2 5.2 28 100 — *outside the scope of the present invention ***outsidea preferred scope of the present invention

In the case of sample number 33, the substitution molar ratio a of Nawas 0.95, and this excessive substitution amount of Na resulted in a lowelectromechanical coupling coefficient k₃₁ of 5%, which is less than10%, and also a piezoelectric constant d₃₃ of 24 pC/N, which is lessthan 30 pC/N, thus failing to exhibit favorable piezoelectricproperties.

It was found in the case of sample number 36 where the substitutionmolar ratio b of Li is 0.20, that the excessive substitution amount ofLi resulted in a low electromechanical coupling coefficient k₃₁ of 4.6%,which is less than 10%, and also a piezoelectric constant d₃₃ of 21pC/N, which is less than 30 pC/N, thus failing to obtain favorablepiezoelectric properties.

In the case of sample number 38 (substitution molar Ta amount c of 0.4)the excessive substitution amount of Ta resulted in a lowelectromechanical coupling coefficient k₃₁ of 5%, which is less than10%, thus failing to obtain favorable piezoelectric properties. Inaddition, it was found that the Curie point Tc of 120° C. is too low touse the sample as a piezoelectric body.

The solid solubility molar ratio x of CaZrO₃ is 0.1 in the case ofsample number 42. It was found that the excessive solid solubilityamount of CaZrO₃ resulted in a low electromechanical couplingcoefficient k₃₁ of 5.2%, which is less than 10%, and also apiezoelectric constant d₃₃ of 28 pC/N, which is less than 30 pC/N, thusfailing to obtain favorable piezoelectric properties. Furthermore, itwas found that the low Curie point Tc of 100° C. is not suitable for useas a piezoelectric body.

In contrast to these samples, sample numbers 31, 32, 34, 35, 37, and 39to 41, had a, b, c, and x values which were respectively 0≦x≦0.06,0≦a≦0.9, 0≦b≦0.1, and 0≦c≦0.3, and these quantities all fill within thescope of the present invention. Thus, the use of Ni for the internalelectrode material and co-firing did not cause defective polarization,and provided such a favorable piezoelectric property as anelectromechanical coupling coefficient k₃₁ of 10% or more and apiezoelectric constant d₃₃ of 30 pC/N or more, and allowing for a Curiepoint Tc of 150° C. or more.

However, the main constituent contained no CaZrO₃ in the case of samplenumber 39, and only one to three of the 16 samples were determined asnon-defective products. Accordingly, CaZrO₃ is preferably made presentas a solid solution in the main constituent from the viewpoint ofproduct yield, and CaZrO₃ is preferably made present as a solid solutionso that the solid solubility molar ratio x in the main constituent is0.001 or more.

EXAMPLE 3

In Example 3, samples different in the content of a specific rare earthelement M3 (M3 element) and samples different in the element species ofthe M3 element were manufactured with Ca for the M2 element and Zr forboth the M4 element and the M4′ element, and evaluated for properties.

First, K₂CO₃, Na₂CO₃, Li₂CO₃, Nb₂O₅, CaCO₃, ZrO₂, MnCO₃, Yb₂O₃, SC₂O₃,In₂O₃, Y₂O₃, Nd₂O₃, Eu₂O₃, Gd₂O₃, Dy₂O₃, Sm₂O₃, HO₂O₃, Er₂O₃, Tb₂O₃,Lu₂O₃, La₂O₃, and, Pr₂O₃ were prepares as ceramic raw materials. Then,the materials were weighed so that α, β, δ, and M3 provided compositionsas shown in Table 3 in the general formula[100{0.98(K_(0.45)Na_(0.53)Li_(0.02))NbO₃−0.02CaZrO₃}+2αNa+(α+β)Zr+5Mn+δM3].

Samples of sample numbers 51 to 72 were manufactured in accordance withthe same method and procedure as in Example 1.

The longitudinal electromechanical coupling coefficient k₃₁,piezoelectric constant d₃₃, and Curie point Tc were measured for theserespective samples of sample numbers 51 to 72, in accordance with thesame method as in Example 1.

Table 3 shows the constituent compositions and the measurement resultsfor sample numbers 51 to 72.

Here, samples were determined as non-defective products in the case ofthe longitudinal electromechanical coupling coefficient k₃₁ being 10% ormore, the piezoelectric constant d₃₃ being 30 pC/N or more, and theCurie point To being 150° C. or more, as in the case of Example 1.

TABLE 3 100{0.98(K_(0.45)Na_(0.53)Li_(0.02))NbO³⁻0.02CaZrO₃} + 2αNa +(α + β)Zr + 5Mn + δM3 Electromechanical Piezoelectric Curie CouplingConstant d₃₃ point Sample No. α β α + β δ M3 Coefficient k₃₁ (%) (pC/N)Tc (° C.) Remarks  51** 0 3 3 0 Yb — — — Defective Polarization   52****1 2 3 0 Yb 17.1 109 240 Warpage   53**** 2.5 2.5 5 0 Yb 20 66 300Warpage 54 1 4 5 0.1 Yb 18.1 117 190 — 55 1 4 5 0.5 Yb 18.4 120 190 — 561 4 5 1.0 Yb 17.2 103 190 — 57 1 4 5 5.0 Yb 16.2 100 180 —   58**** 1 45 10.0 Yb — — — Defective Sintering 59 1 4 5 0.5 Sc 17.5 100 180 ColorPoints 60 1 4 5 0.5 In 18.3 116 180 Color Points 61 1 4 5 0.5 Y 18.6 124190 — 62 1 4 5 0.5 Nd 18.5 121 190 — 63 1 4 5 0.5 Eu 18.3 118 190 — 64 14 5 0.5 Gd 17.8 103 190 — 65 1 4 5 0.5 Dy 18.7 122 190 — 66 1 4 5 0.5 Sm17.2 102 180 — 67 1 4 5 0.5 Ho 18.4 115 190 — 68 1 4 5 0.5 Er 18.2 110190 — 69 1 4 5 0.5 Tb 18.3 114 190 — 70 1 4 5 0.5 Lu 17.8 110 190 — 71 14 5 0.5 La 16.3 105 180 Color Points 72 1 4 5 0.5 Pr 17.4 108 190 —*outside the scope of the present invention ****outside a preferredscope of the present invention

In the case of sample number 51, a sample containing no Na therein withα of 0, failed to form Na₂ZrO₃ in the process of the firing. For thisreason, the use of Ni for the internal electrode material and co-firingformed a segregated phase such as Ni, Mn, or Nb, thereby causingdefective polarization.

In contrast to this sample, the partial content molar quantity α of Zrconsumed in the reaction with Na is 1 to 2.5, the partial content molarquantity β of Zr is greater than the partial content molar quantity αthereof, and the total content molar quantity (α+β) of Zr is 3 to 5 molin the case of sample numbers 52 to 57 and 59 to 72, further, a M3element is used which is specified in the present invention. Thus, itwas found that the use of Ni for the internal electrode material andco-firing resulted in no defective polarization, thereby allowing forthe achievement of a laminated piezoelectric ceramic electroniccomponent which has such favorable piezoelectric properties as anelectromechanical coupling coefficient k₃₁ of 10% or more, apiezoelectric constant d₃₃ of 30 pC/N or more, and has a Curie point Tcof 150° C. or more.

However, when the M3 element (Yb) was excessively present at 10 mol,greater than 5.0 mol, with respect to 100 mol of the main constituent,and as is clear from sample number 58 sufficient sintering was not ableto be carried out, thus resulting in a sample with defective sintering.Accordingly, it was found that in the case of containing the M3 element,the M3 element is preferably 5.0 mol or less with respect to 100 mol ofthe main constituent.

Sample numbers 52 and 53 containing no M3 element, and the ceramicsintered bodies exhibited warpage. Accordingly, while a favorablepiezoelectric property and a Curie point Tc of 150° C. or more can beachieved even the M3 element, it was confirmed that it is preferable tocontain the M3 element within the range of 0.1 mol to 5.0 mol withrespect to 100 mol of the main constituent as shown in the case ofsample numbers 54 to 57, in order to prevent the ceramic sintered bodiesfrom having warpage.

In the case of using Sc, In, or La among the M3 elements, the ceramicsintered body had no warpage, but there were color points. This issupposed to be because Sc, In, and La are slightly inferior insinterability as compared with the other M3 elements. There is apossibility that the color points will lead to degraded reliability ofpiezoelectric ceramic electronic components. Accordingly, it is morepreferable to use, as the specific rare earth element M3, Yb, Y, Nd, Eu,Gd, Dy, Sm, Ho, Er, Tb, Lu, and Pr excluding Sc, In, and La.

EXAMPLE 4

In Example 4, samples in which part of Nb is substituted with Sb ratherthan Ta were manufactured with Ca for the M2 element, Zr for both the M4element and the M4′ element, and further Yb for the M3 element, andevaluated for properties.

First, K₂CO₃, Na₂CO₃, Li₂CO₃, Nb₂O₅, Sb₂O₅, CaCO₃, ZrO₂, MnCO₃, andYb₂O₃ were prepared as ceramic raw materials. Then, the materials wereweighed so that d provided compositions as shown in Table 4 having thegeneral formula[100{0.98(K_(0.45)Na_(0.53)Li_(0.02))(Nb_(1-d)Sb_(d))O₃−0.02CaZrO₃}+2Na+3Zr+5Mn+0.5 Yb].

Then, samples of sample numbers 81 to 83 were manufactured in accordancewith the same method and procedure as in Example 1.

Next, the longitudinal electromechanical coupling coefficient k₃₁,piezoelectric constant d₃₃, and Curie point Tc were measured for theserespective samples of sample numbers 81 to 83, in accordance with thesame method as in Example 1.

Table 4 shows the constituent compositions and the measurement resultsfor sample numbers 81 to 83.

As in the case of Example 1, samples were determined as non-defectiveproducts when having a longitudinal electromechanical couplingcoefficient k₃₁ of 10% or more, piezoelectric constant d₃₃ of 30 pC/N ormore, and Curie point Tc of 150° C. or more.

TABLE 4 100{0.98(K_(0.45)Na_(0.53)Li_(0.02))(Nb_(1−a)Sb_(d))(O₃ −0.02CaZrO₃} + 2Na + 3Zr + 5Mn + 0.5Yb Electromechanical PiezoelectricCurie Sample Coupling Constant d₃₃ point No. d Coefficient k₃₁ (%)(pC/N) Tc (° C.) Remarks 81 0.01 15.3 70 240 — 82 0.05 14.3 83 150 —83***** 0.10 — — — Defective Sintering *****outside preferred scope ofthe present invention

In the case of sample number 83, having a substitution molar amount d ofSb is 0.10, it was found the excessive substitution amount of Sb causeddefective sintering, thus failing to obtain desired piezoelectricproperties.

In contrast to sample 83, the substitution molar amount d of Sb is 0.05or less in the case of sample numbers 81 and 82, and thus it was foundthat the use of Ni for the internal electrode material and co-firingcaused no defective polarization or defective sintering, therebyallowing for the achievement of a laminated piezoelectric ceramicelectronic component which has such favorable piezoelectric propertiesas an electromechanical coupling coefficient k₃₁ of 10% or more and apiezoelectric constant d₃₃ of 30 pC/N or more, and has a Curie point Tcof 150° C. or more.

INDUSTRIAL APPLICABILITY

The use of Ni for the internal electrode material and the co-firingcause no defective polarization, thereby allowing for the achievement ofa lead-free piezoelectric ceramic composition which has a favorablepiezoelectric property.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   1 piezoelectric ceramic body    -   2a, 2b external electrode    -   3a to 3g internal electrode

The invention claimed is:
 1. A piezoelectric ceramic compositioncomprising a main constituent represented by the compositional formula{(1−x)(K_(1-a-b)Na_(a)Li_(b))(Nb_(1-c-d)Ta_(c)Sb_(d))O₃}−xM2M4O₃}wherein M2 is at least one member of the group consisting of Ca, Ba, andSr, M4 is at least one member of the group consisting of Zr, Sn, and Hf,0≦x≦0.06, 0≦a≦0.9, 0≦b≦0.1, 0≦c≦0.3, and 0≦d≦0.05, and as accessoryconstituents, 2α mol of Na, (α+β) mol of M4′, γ mol of Mn and δ mol ofM3, with respect to 100 mol of the main constituent, wherein M4′ is atleast one member of the group consisting of Zr, Sn, and Hf, M3 is atleast one member selected from the group of Sc, In, Yb, Y, Nd, Eu, Gd,Dy, Sin, Ho, Er, Tb, Lu, La, and Pr, 0.1≦α≦β, 1≦α+β≦10, 0≦γ≦10, and0≦δ≦5.
 2. The piezoelectric ceramic composition according to claim 1,wherein 2≦γ≦10.
 3. The piezoelectric ceramic composition according toclaim 2, wherein 0.001≦x≦0.06.
 4. The piezoelectric ceramic compositionaccording to claim 3, wherein 0<d.
 5. The piezoelectric ceramiccomposition according to claim 4, wherein 0<δ.
 6. The piezoelectricceramic composition according to claim 5, wherein 0.1≦δ.
 7. Thepiezoelectric ceramic composition according to claim 6, wherein M3 is atleast one member selected from the group of Yb, Y, Nd, Eu, Gd, Dy, Sm,Ho, Er, Tb, Lu, and Pr.
 8. The piezoelectric ceramic compositionaccording to claim 1, wherein 0.001≦x≦0.06.
 9. The piezoelectric ceramiccomposition according to claim 1, wherein 0<d.
 10. The piezoelectricceramic composition according to claim 1, wherein 0<δ.
 11. Apiezoelectric ceramic electronic component comprising a sinteredpiezoelectric ceramic body comprising internal electrodes andpiezoelectric ceramic layers stacked alternately; and at least twoexternal electrodes on a surface of the piezoelectric ceramic body,wherein the piezoelectric ceramic layers comprise the piezoelectricceramic composition according to claim
 9. 12. The piezoelectric ceramicelectronic component according to claim 11, wherein the internalelectrodes comprise Ni as their main constituent.
 13. A piezoelectricceramic electronic component comprising a sintered piezoelectric ceramicbody comprising internal electrodes and piezoelectric ceramic layersstacked alternately; and at least two external electrodes on a surfaceof the piezoelectric ceramic body, wherein the piezoelectric ceramiclayers comprise the piezoelectric ceramic composition according to claim8.
 14. The piezoelectric ceramic electronic component according to claim13, wherein the internal electrodes comprise Ni as their mainconstituent.
 15. A piezoelectric ceramic electronic component comprisinga sintered piezoelectric ceramic body comprising internal electrodes andpiezoelectric ceramic layers stacked alternately; and at least twoexternal electrodes on a surface of the piezoelectric ceramic body,wherein the piezoelectric ceramic layers comprise the piezoelectricceramic composition according to claim
 7. 16. The piezoelectric ceramicelectronic component according to claim 15, wherein the internalelectrodes comprise Ni as their main constituent.
 17. A piezoelectricceramic electronic component comprising a sintered piezoelectric ceramicbody comprising internal electrodes and piezoelectric ceramic layersstacked alternately; and at least two external electrodes on a surfaceof the piezoelectric ceramic body, wherein the piezoelectric ceramiclayers comprise the piezoelectric ceramic composition according to claim2.
 18. The piezoelectric ceramic electronic component according to claim17, wherein the internal electrodes comprise Ni as their mainconstituent.
 19. A piezoelectric ceramic electronic component comprisinga sintered piezoelectric ceramic body comprising internal electrodes andpiezoelectric ceramic layers stacked alternately; and at least twoexternal electrodes on a surface of the piezoelectric ceramic body,wherein the piezoelectric ceramic layers comprise the piezoelectricceramic composition according to claim
 1. 20. The piezoelectric ceramicelectronic component according to claim 19, wherein the internalelectrodes comprise Ni as their main constituent.
 21. A piezoelectricceramic electronic component comprising a sintered piezoelectric ceramicbody comprising internal electrodes and piezoelectric ceramic layersstacked alternately; and at least two external electrodes on a surfaceof the piezoelectric ceramic body, wherein the piezoelectric ceramiclayers contain a main constituent and an accessory constituent, theaccessory constituent contains 2α mol of Na with respect to 100 mol ofthe main constituent, and wherein molar content of respective elementsconstituting piezoelectric ceramic layers are represented by:x=Σ(Ca,Ba,Sr)/(Σ(Nb,Ta,Sb,Ca,Ba,Sr),a=1−(Σ(Li)/(Σ(Nb,Ta,Sb)−(Σ(K)/(Σ(Nb,Ta,Sb)), b=Σ(Li)/Σ(Nb,Ta,Sb),c=Σ(Ta)/Σ(Nb,Ta,Sb), d=Σ(Sb)/Σ(Nb,Ta,Sb),α=50×(Σ(K,Na,Li))/Σ(Nb,Ta,Sb,Ca,Ba,Sr)−Σ(Nb,Ta,Sb)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)),α+β=100×(Σ(Zr,Sn,Hf)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)−Σ(Ca,Ba,Sr)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)),γ=100×(Σ(Mn)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)), andδ=100×(Σ(Sc,In,Yb,Y,Nd,Eu,Gd,Dy,Sm,Ho,Er,Tb,Lu,La,Pr)/Σ(Nb,Ta,Sb,Ca,Ba,Sr)),in which Σ( . . . ) indicates the total of moles of the elements withinthe brackets ( ), 0.001≦x≦0.06, 0≦a≦0.9, 0≦b≦0.1, 0≦c≦0.3, 0≦d≦0.05,0.1≦α≦β, 1≦α+β≦10, 0≦γ≦10, and 0≦δ≦5.
 22. The piezoelectric ceramicelectronic component according to claim 21, wherein the internalelectrodes comprise Ni as their main constituent.